| There
is a lot
of interest
in Part 2
of my essay
on "Grid
Designer
Dangers".
It's coming.
We want to
do the topic
justice, and
we want to
reflect the
improved
grid designing
capabilities
of our new
3.3.0.1 release. We'll
publish Part
2 in a week or two at the most. |
- I
added an external configuration
file but it doesn't seem
to be having any effect
on the application. Is the
app using the new file
or the old, embedded
file?
- My application
was running fine. Then
I added a grid
which I filled
with a few hundred items
and suddenly it's balky
and slow. What happened?
- I've instrumented
my code with messages
that I am writing
to the DevForce debug
log. I know I can see
the log in a browser.
But I always have to
refresh it. Can I watch
the log change as the
events happen?
You
may know already that
DevForce publishes many
routine messages to your
application's DebugLog.
The standard messages
concern configuration
file discovery, assembly
discovery, and every
attempt to access the database. You can supplement the DevForce messages with custom
messages of your own.
The
DebugLog itself is an
XML file that resides
in your executable directory
by default.
I
can double-click the
log to view it in a browser
which will render it
in reasonable fashion,
thanks to its companion
CSS and XSL files. That's
great for a post-mortem
but a little hard to
use if you want to watch
log updates as they
happen.
I
Need the DevForce TraceViewer
The
TraceViewer is a DevForce
mini-application that
gives me a live view
of the debug log. I
can launch the TraceViewer within
my application and see
each message as it is
posted to the log.
Here's a snapshot of the TraceViewer showing custom messages from
my application login.
Here
is a message showing that
the application found the
DevForce configuration
file, IdeaBlade.ibconfig,
in the AppHelper assembly
after looking first in
the executable directory
and then inside the executing
assembly.
The
record of database access
attempts is essential for
understanding performance
problems, especially in
grids. Here we see
the fetch of all Employees.
Later
we see the DevForce
persistence layer fetch
the Orders of a single
Employee.
If
the command is too long
to view in the grid, we
can double-click the message
cell and see the message
in a dialog.
Using
TraceViewer Information
to Resolve Problems
Suppose
our application displays
a grid with hundreds
of Employees. Each
grid row includes a digest
of an employee's orders
- the number of orders,
the customers, the total
dollar values, etc.
If
we code the grid in a naive
way, with no attention
to performance, we will
see a flurry of entries
in the TraceViewer. Every
time the user scrolls from
one employee grid line
to the next, we see a new
flurry. The messages will
really fly if the user
clicks a column header
to sort the grid.
We
scroll back through the
messages and see the problem. DevForce
is making a lot of little
trips to the database.
There is a trip for each
employee's orders. There's
another trip for each employee
order's customer. There's
another trip for each employee order's
item details. No wonder
the application is a dog.
There
was nothing wrong with
our original naive implementation
per se. Our first goal
should be to make the application
work using the simplest
approach necessary. We
accomplished that goal.
We were not going to anticipate
a performance problem before
we had a performance problem.
Now that
we have performance problem,
the TraceViewer helps
us identify it quickly
so we can fix it.
Fortunately,
the fix is easy: we add
spans to the query so that
DevForce makes a single
request to fetch all
of the employee, order,
customer, and item detail
data that we know we're
going to display in the
grid. Problem solved.
Note:
Span queries are a topic for another Tech Tip. You can read about
them in our Developers' Guide. |
Add
the TraceViewer to Your
Program
It's
incredibly easy to do.
- In
your start-up project,
add a reference to IdeaBlade.UI.WinForms.PlatformControls.
- Open
your start-up class (typically
Program.cs or Program.vb).
- Find
the static Main method (Shared Main in VB).
- Make
some room just below
any calls to the Application class (e.g., Application.EnableVisualStyles()).
- Add
the following code to
show the TraceViewer.
// C#:
IdeaBlade.UI.WinForms.PlatformControls.TraceViewerForm traceForm;
traceForm = new IdeaBlade.UI.WinForms.PlatformControls.TraceViewerForm();
traceForm.Show();
'
VB.NET:
Dim traceForm As _
New IdeaBlade.UI.WinForms.PlatformControls.TraceViewerForm()
traceForm.Show()
That
is all there is to it.
Next time you launch
your application, the
TraceViewer will appear,
followed shortly thereafter
by your application's
main window. You can
toggle between the two
windows at will.
Why
Don't I Just Use SQL
Profiler?
Use SQL Profiler by all means. It's a fantastic
tool for monitoring
database activity dynamically
in much the same was
as you use the TraceViewer.
You still want to launch the TraceViewer
for a number of reasons,
including:
- Your application launches the TraceViewer
for you; you have to remember to launch the SQL Profiler.
- The SQL Profiler only
tells you about database activity; the TraceViewer
captures other application activity in addition to
database activity.
- You can customize the
messages in the TraceViewer so you can see what part
of your application results in a specific database
request.
Conclusion
The
TraceViewer is a critical development tool that's easy
to run. I add the TraceViewer to my application within the first five minutes of coding.
It's a great habit to
get into; make it one
of yours.
- The
TraceViewer runs
in the same process
as your application.
You can run it in
a separate process
if you prefer. It
takes a tiny bit
more work; see the
Developers' Guide
for more information.
- You
can close the TraceViewer
without shutting
down your application.
- I
don't want my customer
to see the TraceViewer.
I wrap those launch
lines in compiler
debug directives
so the TraceViewer
never shows in release
mode.
- N-tier deployment results in a slightly different approach to logging.
The Developers' Guide
can tell you more.
|
